Acl and block domains-..

[Michael Fernández "M." <mfernandez@xxxxxxxxx>]

Hi.. 

i use Squid + SquidGuard

i have groups.. 

A= 10.0.20/28
B= 10.0.21/28
C= 10.0.22/28

so i want block webmessenger.msn.com, and many others sites for groups A
and B, but not for C

Somebody know how can i do it?

Thanks!!! a lot!

Michael.-